When a semiconductor substrate or a liquid crystal panel is microprocessed by using a plasma, it is extremely crucial to control, for example, a temperature distribution, a plasma density distribution and a reaction product distribution on the substrate to be processed. If such distributions are not properly controlled, it is difficult to secure process uniformity on a surface of the substrate, thereby deteriorating a production yield of a semiconductor device or a display device.
Generally, a mounting table (support table) for mounting thereon a substrate to be processed inside a chamber of a plasma processing apparatus functions as a high frequency electrode for applying a high frequency power to a plasma space, as a support member for supporting a substrate, e.g., by an electrostatic adsorption and as a heat plate for controlling the substrate at a predetermined temperature by heat conduction. The mounting table serving as the heat plate is required to properly compensate a heat distribution caused by a substrate supporting structure or a heat input characteristic distribution on the substrate caused by nonuniformity of a radiant heat from a plasma and a chamber wall.
Conventionally, in order to control a temperature of a mounting table, there has been widely used a method for supplying a coolant whose temperature is controlled by a chiller unit into a coolant channel (passageway) provided inside the mounting table to be circulated therein. Since the chiller unit is disposed in a facility area separately provided from a clean room where a processing apparatus is installed, the length of a line for connecting the chiller unit and the mounting table in the chamber can be at least a few meters and sometime can exceed 10 m.
Recently, in a plasma processing, a trend towards miniaturization and diversification of processing requires various profiles for a temperature distribution of a mounting table. However, in most applications, a temperature control is required to have a proper balance between a central portion and a peripheral portion of the mounting table to achieve an in-surface uniformity of the processing performed on a substrate. As for a prior art capable of meeting such demand, there is known a technique for supplying coolants whose temperatures are controlled independently by two chiller units into coolant channels respectively provided at a central portion and at a peripheral portion in the mounting table to be circulated therein, thereby independently controlling respective temperatures of the central portion and the peripheral portion of the mounting table (see, e.g., Japanese Patent Laid-open Application No. H6-37056).
However, the aforementioned prior art requires two chiller units, which is inefficient in terms of cost and space and further has poor responsiveness in a temperature control. In other words, since a thermal capacity of the chiller unit itself is considerably large, it is difficult to rapidly change a temperature of a coolant. Moreover, due to a considerably long length of the line (channel) from the chiller unit to the mounting table, the temperature can neither be raised nor lowered at a high speed. Recently, for example, a plasma etching process requires a method for successively processing a multilayer film on a substrate to be processed inside a single chamber instead of multiple chambers used conventionally. In order to implement such method by using a single chamber, at a time of changing a target film, it is essential to have a technique to change a temperature of the substrate in a short period, i.e., a technique to raise or lower the temperature of the mounting table at a high speed.
In addition, a method may be proposed for controlling a temperature distribution of a mounting table by a heating element, e.g., a heater, a thermally conductive element or the like, embedded in the mounting table. However, this method raises a running cost, can influence on a function of a high frequency electrode and complicates an inner structure of the mounting table and, therefore, it is impractical.